Process of depositing gold from its aqueous solutions



(No Model.) I 2 Sheets-Sheet 1.

e H. K. B. DAVIS. PROCESS OF- DEPOSITING GOLD FROM ITS AQUEOUSSOLUTIONS.

No. 546,113. Patented Sept. 10,1895.

'W-ITNESSESL INVENTOR ANDREW 5.6RAI1AM.PHOTDUTHQWASNINGTONDC v v 2Sheets-Sheet 2.

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H. K. B. DAVIS. mocnss 0F DEPOSITING GOLD FROM ITS AQUEOUS SOLUTIONS.

No. 546,113. PatentedSept. 10, 1895.

ANDRlW BJZRANANL PNOTWUDIQWASNINQTDN D C HENRY K. B. DAVIS, orPHILADELPHIA, PENNSYLVANIA.

PROCESS OF DEPOSlTlNG GOLD FROM ITS AQUEOUS SOLUTIONS.

SPECIFICATION forming part of Letters Patent No. 546,113, datedSeptember 10, 1895.

Application filed April 25, 1895. Serial No.'547,116. (No specimens.)

To all whom it may concern.-

Beit known that I, HENRY K. B. DAVIS, of the city of Philadelphia andState of Pennsylvania, have invented certain new and useful Improvementsin the Process of Depositing Gold from itsAqueous Solutions, of whichthe following is a specification.

The accompanying drawings illustrate two types of apparatus adapted tothe conduct of my process, Figure 1 being a vertical central sectionthrough a preferred form of such apparatus, and Figs. 2 and 3being,respectively, a partial vertical central section and a transversesection of a modified form, the sectional plane of Fig. 3 beingindicated by the lines 3 3 in Fig. 2. It must be understood, however,that the invention is not restricted to the employment of these or anyparticular form of apparatus, and that the types shown in the drawingsare merely for convenience of illustration.

My improvements relate particularly to that process of depositing goldwhich consists in subjecting the solution of its chloride or chlorides,to the action of carbon, substantially in the manner set forth inLetters Patent of the United States No. 227,963, dated May 25, 1880. Ihave discovered that the rapidity and completeness of deposit of thegold upon the carbon can be enormously increased by diffusin gfreehydrogen gas through the gold solution during, or just previous to, itspassage through the carbon, and the utilization of this discovery, in anorganized man ner, constitutes the subject of my invention.

I will now proceed to describe, by reference to Fig. 1 of theaccompanying drawings, a convenient and economical method for theapplication of my process. In said figure, A

represents a cylind rical vessel, usually of iron,

having alead1ining,(indicated at a.) Said vessel is provided near itsbottom with an outlet pipe 13, controlled by means of a stop-cock b,

and is also provided with an inlet or deliverypipe 0, similarlycontrolled by the stop-cock O, and leading from any convenient source ofsupply of the gold solution. The vessel A is partly filled with carbon,as indicated at D, charcoal in small pieces of uniform size beingpreferably employed for this purpose. Upon the top of the mass ofcharcoal is a perforated leaden plate E, whose purpose is to prevent toogreat disturbance of the charcoal by the inflowing liquid, and abovesaid plate is a layer of zinc shavings F.

The solution of gold chlorides which I employ usually contains an excessof chlorine, and also, as an incident of manufacture, a slight excess,say one per cent, of free sulphuric acid. In cases, however, where suchpercentage of sulphuric acid is lacking, and where the above-describedapparatus is to be employed, such acid should be added in about theproportion above mentioned. This solution is run into the vessel A andallowed to pereolate down through thelayer of zinc shavings F, andthence through the mass of charcoal D, the filtered liquid being finallydischarged at theoutlet-pipe B. In practice I prefer to admit thesolution in sufficient quantity to keep the layer of zinc shavingsentirely submerged, as indicated at G. Thereactions which occur Ibelieve to be as follows:

The attack of the sulphuric acid upon the zinc shavings is attended withan evolution of hydrogen gas, which immediately combines with thechlorine in the gold solution to form hydrochloric acid, thussettingfree the metallicgold, which is deposited in the usual manner upon thesurface of the charcoal. The resultant sulphate of zinc and hydrochloricacid both pass away in aqueous solution through the charcoal and aredischarged at the outlet-pipe B.

To guard against any possible loss of gold by reason of a too free orrapid passage through the charcoal, I prefer to discharge the liquorfrom the above-described vessel into another similar one; but this, ofcourse, is a mere detail of practice and need not be further described.

It will be noted that in the above application of my process I provide ameans for directly generating hydrogen gas from the water of the goldsolution itself at the moment of its entry into the charcoal, and that,incidentally, I take advantage ofa usual ingredient of the chloridesolution.

Vhile I deem this application of my process the most economical andconvenient for use, I do not limitmy claims thereto, as it is obviousthat a similar reaction could be obthe rate of percolation.

tained by generating the hydrogen gas elsewhere and admitting it tocontact with the gold solution, either during the passage of the latterthrough the charcoal, or as the immediate preliminary to such passage,the only limitations in this direction being economical and convenientconditions of manufacture. Thus in the type of apparatus shown in Figs.2 and 3, A indicates the vessel containing carbon D, a being thelead-lining of the vessel. Immediately above the mass of car bon is aspiral coil of lead pipe H, having numerous fine perforations h. Saidpipe 11 leads from a generator I, located at any con- Venient point inwhich hydrogen gas is to be developed by any convenient process, with apressure and volume sufficient to cause the discharge of the gasthroughout the perforated portion of the pipe H. The gas thus escapingpermeates the gold solution, (indicated by the dotted lines in the upperportion of the vessel A,) which solution is of course supplied throughthe pipe C in conformity with It is of course desirable to diifuse thehydrogen throughout the solution to the greatest possible extent, and tothis intent a perforated pipe, similar to the pipe H, may be withadvantage located within the feeding-reservoir for the solution, thehydrogen from a generator, such as I, being freely admitted through thesame.

I do not claim, broadly, the use of hydrogen gas to decompose goldchlorides, for I am of course aware that, as a matter of laboratoryknowledge, its capacity to do so has been recognized. For commercialpurposes, however, such method is not practicable, and it is only byreason of the organized employment of hydrogen treatment in combinationwith the carbon process, as herein set forth, that the properties ofhydrogen in this respect become substantially available.

Having thus described my process, I claim- 1. As an improvement in theprocess of depositing gold from the aqueous solution of its chloride,thehereinbefore described process of diffusing hydrogen gas through saidsolution and passing said solution through carbon, substantially asdescribed.

2. The hereinbefore described process of depositing gold from theaqueous solution of its chloride, which consists in forming an acidexcess in said solution; passing said solution over a metal, such aszinc, and thereby generating hydrogen gas in said solution, and thenpassing said solution through carbon, substantially as described.

HENRY K. B. DAVIS. \Vitnesses:

JAMEs H. BELL, G. HERBERT JENKINS.

